Study And Application Of Polarographic Catalytic Wave Of 1,4-Benzodiazepine And Corticosteroids

Polarographic catalytic wave of organic compounds is mainly classed to two variations, the parallel catalytic wave and the catalytic hydrogen wave. The catalytic hydrogen wave is ascribed to the fact that certain substances containing nitrogen or sulfur can diminish the hydrogen overvoltage and accelerate hydrogen ion discharge at more positive potential on the cathode. As for the parallel catalytic wave, it is attributed to the fact that the intermediate free radical produced during the reduction process of organic compounds is oxidized by oxidant to regenerate the original. Obviously, the free radical is concerned in the study of polarographic catalytic wave of organic compounds, therefore, it is of great significance for electroanalytical chemistry, biology and pharmacology. Study on the catalytic wave has been paid more attention on the catalytic hydrogen wave of protein abroad, but other kinds of catalytic wave were rarely reported.In this thesis, the parallel catalytic waves of diazepam and chlordiazepoxide (belongs to the group of 1,4-benzodiazepine )-, prednisone and dexamethasone (corticosteroids) and polarographic kinetic wave of atropine in the presence of oxidant are observed. Furthermore, the mechanism that produce the parallel catalytic waves is studied. Additionally, it is applied to analytical determination of medicament. This thesis consists of six parts:Part one Review of study on electrochemistry of 1,4-benzodiazepine and corticosteroidsPart two Study and application of polarographic catalytic wave of chlordiazepoxidePolarographic catalytic wave of chlordiazepoxide in the presence of K^Og was studied in aqueous and DMF/HaO mixed solutions. The results showed that the reduction of the N=C bond in 1,2-position of chlordiazepoxide via an intermediate free radical in two one-electron successive additions hi alkaline medium. When K2S2O8 was present, the free radical of the N=C bond was oxidized to regenerate the original, producing a parallel catalytic wave of chlordiazepoxide. It was determinedthat the apparent rate constant kf of the catalytic reaction is 3.2 X 103 mol-1 L s-1. Using the catalytic wave can determine trace of chlordiazepoxide by linear-potential scan polarography. In 0.12 mol/L NH3 / NH4Cl (pH 10.2 0.1) / 0.016 mol/L K2S208 supporting electrolyte, the second-order derivative peak current of the catalytic wave was rectilinear to chlordiazepoxide concentration in the range of 3.20 X 10"8~ 1.60 X 10-7, 1.60 X 10-7~1.44 X 10'6 and 1.44 X 10-6 ~1.44X 10-5 mol/L, respectively. The limit of detection was 9.0 X 10"9 mol/L. Part three Study and application of polarographic catalytic wave of diazepamA new method for the determination of diazepam was proposed based on its polarographic catalytic wave in the presence of persulfate. In 0.10 mol/L NaAc-0.10 mol/L HAc(pH 4.7) -0.02 mol/L K2S2Og supporting electrolyte, diazepam yielded a polarographic catalytic wave with peak potential -0.89 V (vs. SCE). The well-defined second-order derivative peak of the catalytic wave was obtained by linear-potential scan polarography. The peak current of the catalytic wave was linear to diazepam concentration in the range of 5.6 X 10" ~2.0 X10"4 mol/L. The detection limit was 9.6 X 1O"9 mol/L. The peak current of the catalytic wave was 15 tunes higher than that of the corresponding reduction wave for 4.0 X 10"6 mol/L diazepam. The proposed method was used to determine the diazepam contents in pharmaceutical tablets. The mechanism of the polarographic catalytic wave of diazepam was discussed. It was determined that the apparent rate constant &t of the catalytic reaction is 6.74X 103 mol"1 L s".1 Part four Study and application of polarographic catalytic wave of prednisoneA polarographic catalytic wave of prednisone in the presence of K2S2Og was observed. When K2S2Ogwas present, the free radical from one electron reduction of the A 1>4-3 keto group of prednisone was oxidized by S2Og2" to regenerate the original keto group, producing a polarographic catalyti...